Help using subfunction to compute zeros of a function

Question

Steven 2012-4-1

评论： Krishant 2024-3-11

I need help with creating a function with a subfunction to compute the zeros of a problem over a certain interval.

For example: 3x^3 - 12x^2 - 33x + 80 over -10 < x < 10

I want to find the all the zeros for that interval but every function I try it doesn't work. Here's my code so far:

function yzero = findzeros(range)

fun=@testfun;

[yzero,value]=fzero(fun,range);

function fx = testfun(x)

fx=(3.*x.^3)-(12.*x.^2)-(33.*x)+80;

end

end*

This only get it to compute one zero though but I graphed it on my calculator and there are 3 zeros over the interval.

Please Help me with finding a function that works!

Walter Roberson 2012-4-1

Duplicate is at http://www.mathworks.com/matlabcentral/answers/34133-finding-zeros-of-an-equation

Krishant 2024-3-11

Use a primary function with a subfunction to compute the zeros of the function 3𝑥 3 − 12𝑥 2 − 33𝑥 + 80 over the range −10 ≤ 𝑥 ≤ 10.

Answer 1

Taniadi 2012-4-1

you can use fzero or fsolve to solve the problemm but it is necessary that you change initial guess to get 3 roots.

Steven 2012-4-1

any suggestions on how I can do this?